Language
Using Language
• What is language for?
Using Language
• What is language for?
– Rapid, efficient communication
• To accomplish this goal, what needs to happen
in the brain?
Understanding Linguistic Input
• To accomplish this goal, what needs to happen in
the brain?
– Encode input (speech, writing, other?)
• Make neural representation(s)
– transform the input (e.g. written word to internal
sound)
• This probably involves many intermediate steps
– Associate input with meaning – access the lexicon
• Lexicon – a mental representation of the meaning of words
– Mental dictionary is a poor but useful analogy
Written Input
• Some terms:
– Orthography – visual form of a word
• Non-trivial problem! Like all objects, words can have
many different instances of the same item
• bird bird bird bird bird bird
Written Input
• Visual Word Form Area
(WFA) is specialized for
representing written
words
– Words are not just pictures
– Specialization may be related to
the need to “overcome” mirrorinvariance
• E.g. b, p, d are all different
letters but
Are all the same object !!
Dehaene (2009)
Spoken Input
– Phonology – how the word sounds; acoustic
• Words are comprised of acoustic speech units called phonemes
Spoken Input
– Phonology – how the word sounds; acoustic
• Phonemes are not invariant – different acoustic inputs are
“mapped” onto the same phoneme
Spoken Input
• The Segmentation Problem:
– The stream of acoustic input is not physically segmented into discrete phonemes, words,
phrases, etc.
– Silent gaps don’t always indicate (aren’t perceived as) interruptions in speech
Spoken Input
• The Segmentation Problem:
– The stream of acoustic input is not physically segmented into discrete phonemes, words,
phrases, etc.
– Continuous speech stream is sometimes perceived as having gaps
Spoken Input
• The Segmentation Problem:
– How do we solve the segmentation problem? Overlay
additional information:
• Prosody
– Inflection, syllabic stress, pauses
Spoken Input
• The Segmentation Problem:
– How do we solve the segmentation problem? Overlay
additional information:
• Vision
– Read lips!
– Demonstrated by the McGurk effect
Functional Anatomy of Spoken Input
• Note that the low-level
auditory pathway is not
specialized for speech
sounds
– Both speech and non-speech
sounds activate primary
auditory cortex (bilateral
Heschl’s Gyrus) on the top of
the superior temporal gyrus
Functional Anatomy of Spoken Input
• Which parts of the auditory pathway are specialized for
speech?
• Binder et al. (2000)
– fMRI
– Presented several kinds of stimuli:
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•
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•
•
white noise
These have non-word-like acoustical properties
pure tones
non-words
These have word-like acoustical properties but no
reversed words
lexical associations
real words word-like acoustical properties and lexical associations
Functional Anatomy of Spoken Input
• Relative to “baseline” scanner
noise
– Widespread auditory cortex
activation (bilaterally) for all
stimuli
– Why isn’t this surprising?
Functional Anatomy of Spoken Input
• Statistical contrasts reveal specialization for speech-like
sounds
– superior temporal gyrus
– Somewhat more prominent on left side
Functional Anatomy of Spoken Input
• Further highly sensitive contrasts to identify specialization for
words relative to other speech-like sounds revealed only a
few small clusters of voxels
• Brodmann areas
– Area 39
– 20, 21 and 37
– 46 and 10